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0026:.'3 Effects Matrix Process and Assumptions In the November Technical Work Oroup Meeting (November 4-5 1997) a portion of the meeting was devoted to discussion about potential high inflows to Lake Powell and subsequent releases from Olen Canyon Dam higher that 25,000 cfs. Included in this discussion was the possibility of implementing short duration, experimental high flows (Beach Habitat Building Flows: BHBF) as a resource management strategy. The course of the discussion led to the recognition that the TWO needed to develop a process to evaluate the resources and a rating to establish the effects between January to June 1998 of a 45,000 cfs release, to assist in the decision-making process concerning which month to run a BHBF. The recommended process involved compiling the expert opinions and research citations supporting that opinion of scientists experienced with the Colorado River ecosystem, and providing a matrix that used a 7-point rating scale (positive, negative, no effect). In addition, resource impacts should be considered relative to the hydrologic trigger before and after the BHBF, because most spills and BHBF will occur during high flow years. Comments were made by some TWO members that the matrix needed to be more comprehensive, however, the degree to which the matrix should be further developed was not defined by TWG members and is an issue that need further development and consideration. The TWO recommended that OCMRC use this process to develop a Resource Effects Matrix for the months of January to June. Assumptions Based on the above criteria, the assumptions for a resource effects matrix are as follows: . A short duration (2-4 days) high flow of 45,000 cfs could take place in months January - June 1998. BHBF occur in high flow years, so expect flows prior to and after a BHBF event <: to be high (20-25 cfs, at least). , . Hydrologic conditions meeting the triggering criteria indicate that there is a high probability of a dam safety related spill. The decision for or against a BHBF does not significantly change the risk of an emergency release later in the season. By implementing a BHBF, the beneficial effects of a spill (e.g., sand storage) can be maximized and the deleterious effects (e.g., biological disturbance) can be mitigated through advanced planning. Directions to Developers of Resource Matrix . . Utilize a 7-point scale that varies from +3 to -3 with 0 representing no effect, +3 being strongly positive and -3 being strongly negative. . The matrix was only for consideration for the year 1998 and it was not intended that a BHBF would be conducted every year. An event such as this is unlikely because the hydrologic trigger would not be met every year. The intent and structure of the matrix only allows for a high flow scenario to be evaluated, as was the recommendation of the TWO to OCMRC (see November minutes). The effects of a